In order to connect aircraft to a satellite network for the transmission of multimedia data, wireless broadband channels for data transmission with very high data rates are needed. For this purpose, antennas need to be installed on the aircraft, which have small dimensions for installation under a radome and nevertheless satisfy extreme requirements in terms of the transmission characteristic for an oriented wireless data communication with the satellite (for example, in the Ku, Ka or X band), since any interference with neighboring satellites has to be reliably ruled out.
The antenna is moreover movable under the radome, in order to update the orientation to the satellites as the aircraft moves. For this purpose, the antenna has to be constructed compactly to remain movable under the radome.
The regulatory requirements pertaining to the transmission operation result from international standards. All these regulatory specifications are intended to ensure that no interference with neighboring satellites can occur in the oriented transmission operation of a mobile satellite antenna.
WO2014005693 and WO2014005699, for example, show solutions for compact antennas for applications in satellite communications. These antennas consist of antenna arrays that are constructed from individual radiators and have suitable feed networks. They can be implemented in different geometries and different length to side ratios, while ensuring high antenna efficiency. In particular, antenna arrays with small installation height can be produced.
WO2014005699 discloses feed networks that can be produced from a combination of waveguides and microstrip lines. The disclosure provides an antenna system comprising microstrip conductor arrangements for feeding individual horn radiators within a module. However, the disclosure suffers from several drawbacks. For example, when the horn radiators are densely packed in antenna arrays, efficient feed networks have to be accommodated in the installation space available behind the horn radiator array. Here, the number of the power dividers required is high. The power dividers in the waveguide area of the feed network require installation space, which is limited.
The feed networks shown in WO2014005699 make it possible to distribute, in the case of signal transmission, a sum signal with correct amplitude and phase over the individual radiators or conversely, in the case of receiving, to add the signals of the individual radiators correctly to a sum signal. The feed network consists of microstrip conductors, which cluster individual radiator groups, and consists of a waveguide network, again to cluster several groups.
Microstrip conductors have the advantage of requiring little space, and thus they allow a high integration density. The disadvantage consists of higher electrical losses compared to waveguides which, however, require a considerably larger volume compared to microstrip conductors.
In order to keep the weight and the rotation volume of an antenna as small as possible for a given aperture surface area, there is a need for minimizing the number of the waveguide sections or the total volume of the waveguide without having to accept trade-offs in the electrical performance of the antenna.